1. Field of the Invention
The present invention relates to a method of manufacturing an electrically-conductive film which is transparent to visible light and useful as a transparent electrode for various display devices and solar cells.
2. Description of the Prior Art
With the development of various display devices and solar cells, demand for electrically-conductive transparent films have been increasing in recent years. Among existing electrically-conductive transparent films of ITO, ZnO, SnO.sub.2 and CdSnO.sub.4 , the ITO-based films are dominant currently because of their low resistivity. However, this type of film has a problem that indium, a component of ITO, is prone to disperse into adjacent films. In the other hand, SnO.sub.2 films, which are chemically stable and low in material cost, have become drawing new attention recently.
Conventionally, the thermal CVD method has been generally used for producing the SnO.sub.2 films, in which a substrate or the whole reaction chamber containing the substrate is heated so that a reactive gas surrounding the substrate is thermally decomposed to form a SnO.sub.2 film on the substrate (refer to U.S. Pat. No. 4,146,657). However, in such conventional SnO.sub.2 film production process since the entire space around the substrate is high in temperature, the thermally decomposed product from the reactive gas would be secondary and tertiary thermally decomposed or would react with the reactive gas which remains decomposed to form a number of bits of various sizes in the formed thin film. Moreover, intense heating of the substrate would cause inaccurate dimensions of the substrate due to distortion, warping and shrinking, deformation of functional structure which has previously been formed on the substrate, and deterioration of the composition of the substrate itself. In addition, because of its outstanding chemical stability, the formed SnO.sub.2 film is highly resistant against the etching process, and therefore it is difficult to make a pattern of thin electrodes.
On the other hand, there has been known a method of forming a thin film by applying a jet of reactive gas onto the substrate surface while heating it by a laser beam so that a thin film is formed by thermal decomposition of the reactive gas, as proposed by one of the inventors of the present invention (refer to Japanese Patent Publications Nos. 59-140366, 59-140367, 59-140368 and 59-140369).